title: Blood-gas CO2 equilibration in lungs of unanesthetized dogs during hypercapnia.
abstract: We have reinvestigated the problem of blood-gas equilibration of CO2 in lungs during hypercapnia. Six dogs with chronic tracheostomy and exteriorized carotid artery were subjected in acute experiments to hypercapnic inspired mixtures [CO2 fraction of expired gas (FICO2) = 0.06; 0.08; 0.10]. Expired CO2 partial pressure (PCO2) was continuously measured with a respiratory mass spectrometer and compared with arterial PCO2 determined in blood samples that were collected during apparent steady-state conditions. Particular care was taken in using continuously recorded temperature in the right heart for correction of blood PCO2 measured by CO2 electrodes. In no animal was there a significant difference between arterial and alveolar PCO2. On the average, this difference was -0.1 Torr at FICO2 = 0.06; 0.0 Torr at FICO2 = 0.08, and -0.2 Torr at FICO2 = 0.10. The results are in agreement with the conventional view that PCO2 in pulmonary capillary blood approaches PCO2 in alveolar gas.
mesh_terms: D000818:Animals; D001831:Body Temperature; D002245:Carbon Dioxide / Q000097:blood*; D004285:Dogs; D005260:Female; D006935:Hypercapnia / Q000097:blood* / Q000503:physiopathology; D008168:Lung / Q000503:physiopathology*; D008297:Male; D011650:Pulmonary Alveoli / Q000503:physiopathology; D011651:Pulmonary Artery / Q000503:physiopathology; D012119:Respiration
chemical_list: D002245:Carbon Dioxide